FEATURES OF THE LABORATORY STAGES OF MANUFACTURING A REMOVABLE PROSTHESIS FROM THERMOPLASTIC MATERIALS
- Authors: Kumskova D.1
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Affiliations:
- Voronezh State Medical University named after N. N. Burdenko
- Issue: Vol 10 (2021): Материалы XVII Международной Бурденковской научной конференции 22-24 апреля 2021 года
- Pages: 395-399
- Section: Стоматология
- URL: https://new.vestnik-surgery.com/index.php/2415-7805/article/view/6524
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Abstract
In orthopedic dentistry, removable and non-removable denture structures are widely used, which serve to replace defects in the dentition of various lengths and restore the functions of chewing and speech.
At the present stage of development of orthopedic dentistry, the requirements for basic materials have increased, the quality of which, to a large extent, determines the functional value of removable dentures. Currently, the market is saturated with a huge variety of basic materials of various quality and technological characteristics.
Recently, technologies for manufacturing removable and non-removable structures made of thermoplastics, which are characterized by the absence of a residual monomer, have appeared on the Russian dental market. They do not contain toxic or allergenic additives, have high biocompatibility and the ability to remember shapes. A high degree of plasticity, accuracy in the manufacture, a wide color gamut to empower and partial removable dentures, splinting, manufacturing immediat-dentures, periodontal prosthesis, tires-dentures and enhance their aesthetic qualities.
Purpose: to justify the use of modern polymer materials in the clinic of orthopedic dentistry for the manufacture of removable dentures.
Materials and methods:
1. To study the main properties of modern dental thermoplastic materials made of nylon used in the clinic of orthopedic dentistry.
2. Improve the laboratory stages of manufacturing removable nylon prosthetics.
Results: 1. To analyze the use of thermoplastic materials used in prosthetic dentistry for bases removable laminar dentures; 2. To study bioinertness polymers for medical purposes; 3. Find out what quality bases removable laminar dentures affects the tissues of the prosthetic bed, the microflora of the oral cavity and durability of the denture; 5.To identify that nylon is the most optimal performance on all kind of thermoplastic materials used in prosthetic dentistry to restore chewing function.
Conclusion: Thermoplastic polymer materials for dental use based on nylon:
- do not contain a residual monomer, which means that they do not subsequently cause a toxic and allergic reaction to the human body as a whole, that is, they have biocompatibility;
- have increased strength;
- have elasticity, shape memory, stability;
- have good aesthetic characteristics;
Thus, as the experience of using these materials has shown, a number of positive properties of thermoplastics allow dentists to expand the indications for the manufacture of many orthopedic structures in the treatment of partial tooth loss, complicated by dental deformities and periodontal diseases.
Full Text
RELEVANCE
To date, the most common thermoplastic polymers are polyamides-nylons. Nylon (silicone) removable dentures, unlike acrylic structures, do not break under excessive or uneven mechanical loads, do not have a microporosity basis for the development of pathogenic microflora in them, do not emit free monomers that are harmful to the body and cause allergies during operation. The advantages of choosing a nylon base for the manufacture of removable silicone prostheses are evidenced by all the following properties:
- aesthetics of almost invisible dentures in the mouth;
- precise fit and reliable fixation of them in the oral cavity, especially strong when using fixing gels;
- quick habituation and the ability to wear it constantly (even during a night's sleep);
- no need to turn the supporting teeth;
- the absence of excessive fluid of the structure and metal elements in it (hooks, clamps, etc.), the ability to cause damage and loosening of the teeth;
- uniformity of the base material, lack of hygroscopicity, immunity to food dyes and absorption of foreign odors;
- the strength of the prostheses and the rational distribution of mechanical loads when chewing only on one side of the jaw.
Removable dentures made of nylon, have sufficient high flexibility, resist fractures.
PURPOSE
To improve the efficiency of production of partially removable prostheses made of thermoplastic materials. Treatment of patients with nylon prostheses.
MATERIALS AND METHODS:
1 For the production of prostheses, a comparative characteristic of all thermoplastic materials was carried out and the most optimal material was selected
2 To study all the laboratory steps for the production of a nylon prosthesis
3 Systematization of all methods of manufacturing a nylon prosthesis
Technology of manufacturing a nylon prosthesis
Clinical stage. The doctor, after preparing the teeth, removes the impression with a perforated spoon. For this purpose, an impression mass is used that does not create pressure on the prosthetic bed (alginate impression mass or low-viscosity silicone impression mass). The dentist should also pay attention to the condition of the gum mucosa, if it is hypertrophied, it is necessary to inform the technician about this.
The laboratory stage. The master model is cast by a dental technician from a supergypse of at least grade 4. In this case, distilled water must be measured with a measuring cup, and gypsum-with a scale, according to the manufacturer's practical recommendations. After the plaster hardens, the dental technician uses a sharp tool on the master model to remove possible bubbles from the surfaces of the teeth and the prosthetic bed. Next, the master model was studied in a parallelometer. To avoid injury to the mucous membrane when using a prosthesis, the undercut on the supporting teeth is blocked with wax. The blocking wax is also applied to critical areas such as the interdental papillae and the hypertrophied mucosa where the dentoalveolar clasps will be located. We duplicate the master model, according to the instructions of the manufacturer of the used duplicate mass. It should be remembered that to obtain exact copies of working models, it is better to use high-quality silicone materials. After curing the silicone mass, the master model is removed from the cuvette and poured into the mold with a supergip, preferably not lower than class 4. It is better to use plaster of a color different from the color of the master model in order not to confuse them in the future. After curing super plasters model is extracted from the mold. The duplicate model and the master model are checked for compliance. The resulting working model, together with the auxiliary one, is installed in the articulator and the boundaries of the future prosthesis are drawn on the working model, while attention is drawn to the unfavorable conditions of the prosthetic bed and measures are taken to eliminate them. When applying the boundaries of the prosthesis to the model, it is important to take into account not only the functional features of the design, but also the aesthetics of the final result. With a large atrophy of the alveolar process, a flat palate, and the severity of the torus, it is necessary to engrave the borders along the distal edge of the prosthesis and in the buffer zones. A wax base is made from a wax plate. On the lower removable prosthesis, the location of the tongue is filled with wax, which is necessary for the casting process.
Clinical stage. The doctor determines the central ratio of the jaws.
The laboratory stage. After making the wax base, they begin setting the teeth. Since nylon does not have a chemical bond with acrylic teeth, therefore, special retention points are created on artificial teeth-retention (diatoric) holes. When preparing retention holes, it is necessary to retreat as far as possible a little further from the base of the tooth. Artificial teeth with retention holes, according to the bite, are installed on the wax base. There must be a layer of wax between the artificial tooth and the alveolar ridge, otherwise the thermoplastic material may not get into the retention holes during injection. After setting the teeth, they begin to model the dentoalveolar clamp, while paying attention to the anatomical possibilities of its location. The areas where the clamps are located are poured with molten wax using a spatula.
The wax base of the prosthesis with the teeth set apart after the end of the modeling of the clasps, is sent to the clinic to check the design and the correctness of determining the central ratio of the jaws.
Clinical stage. The doctor should pay attention to the density of the fit of the base to the mucosa of the prosthetic bed, the correct ratio of the jaws, the setting of artificial teeth, their color, and exclude any inaccuracies in the previous stages.
The laboratory stage. Next, the model is prepared for plastering in a ditch. The teeth are cut off on the working model, without affecting the border of the wax composition. The surface of artificial teeth is cleaned of wax before plastering. The glossy surface should have a wax base. In the main cuvette, the model is cast. The model must be left in the water for 20 minutes before packing. The main cuvettes are treated with vaseline oil. It is necessary to ensure that the oil does not get into the hole for the sprues. Next, we prepare the supergips in the ratios prescribed by the manufacturer, and begin to plaster the model into the lower half of the cuvette. At the same time, all the undercuts formed by the model, gypsum, are isolated. A place is made in the plaster for the passage of the main spigot. Before full plastering, it is advisable to make a gating system from wax. You need to make sure that the gating hole is completely filled with wax. The second half of the cuvette is lubricated with vaseline. We connect the two halves of the cuvette and fix it with four bolts. Bolts are screwed diagonally, to eliminate all possible distortions. The supergip is poured through the upper inlet. After the plaster has frozen, we turn out both bolts diagonally, and the remaining bolts are turned out for two turns and put the cuvette in boiling water for 7 minutes. After warming up the cuvette, we unscrew the two remaining bolts and open the cuvette. Wash out the remaining wax with hot water.
We check whether all the teeth are in place and treat the surface of the mold and counterform with a separating varnish. We make sure that the varnish does not get on the surface of the artificial teeth. After the separating varnish has dried, we connect the cuvette and tighten all the bolts. We prepare the thermostat for operation and the thermoplastics. The cartridge should be kept in the thermostat for 20-30 minutes at a temperature of 36-37 degrees Celsius. This is necessary to remove moisture from the thermoplastics. Cartridges are small (15 grams) and large (25 grams), the choice depends on the size of the prosthesis being manufactured. To avoid the possibility of jamming the injection press heater in the arena, a thin layer of silicone is applied to the cartridge. Make sure that no grease gets into the hole where the thermoplastics are squeezed out of the cartridge, as this will lead to contamination of the material. With the rolled part outwards, the cartridge is placed in the injection machine because at this point the aluminum layer is very thin and the thermoplastics under pressure enter the cuvette and during injection it breaks. After the cartridge is warmed up, the prepared cuvette is inserted into the injection machine.
Processing of a removable prosthesis made of thermoplastics
The recommended rotation speed is 1500 rpm when polishing a nylon prosthesis with diamond heads. Polishing and processing a nylon prosthesis is a bit more difficult than an acrylic one.
After being treated with diamond heads, the prosthesis is treated with sandpaper on a fabric basis of 800-900 grains at 4-5 thousand rpm, and with a brush with natural bristles without pressure at a speed of no more than 3,000 rpm. Silicone polishes are used to treat the edges of the base and interdental spaces. For the final polishing, it is carried out with cotton brushes at a speed of 2,800 rpm with paste.
Storing and applying a removable prosthesis in the oral cavity
It is recommended to immerse the prosthesis in very hot water for 1 minute before storing it, then cool it slightly so as not to cause a burn of the oral mucosa. Facilitates the introduction and application of the prosthesis in the oral cavity heating the prosthesis in hot water, accelerates the process of getting used to the prosthesis. If the dentoalveolar clamp causes pressure on the tissues of the oral mucosa, it is recommended to slightly loosen it, for this you need to place a part of the prosthesis with a clamp in hot water for 1 minute and then slightly bend the clamp. In the same way, you can increase the pressure of the clamp with insufficient fixation of the prosthesis. Correction of the border of the base of the prosthesis is better carried out with a cutter for plastic with large notches or diamond heads tornado "MonAliT" at small revolutions intermittently, so that the material does not melt. Next, the edges of the prosthesis are treated with polishing rubber bands. A more voluminous correction of the base of the prosthesis is better done with a sharp scalpel.
RESULTS
1. Thermoplastic polymer materials for dental use based on nylon: do not contain a residual monomer, that is, they have biocompatibility, are characterized by increased strength, elasticity, shape memory, dimensional stability, and good aesthetic characteristics.
2. A special feature of the clinical and laboratory stages of manufacturing removable structures of prostheses from thermoplastic materials based on nylon is the modeling of the gating system.
3. Based on the above data, the most optimal orthopedic practices are nylon prostheses, which in the oral cavity of the patient, almost do not affect the mucous membrane.
CONCLUSION
Based on these data, the most optimal for the manufacture of prosthetics are thermoplastic materials. This material does not cause an allergic reaction, which contributes to a favorable environment in the oral cavity. For casting bases from nylon, as a rule, one spigot is formed. For casting thermoplastic materials based on nylon, it is necessary to use universal injection machines of various types. The results of thermoplastic materials made of nylon, showed the possibility of their use in the clinic of orthopedic dentistry.
About the authors
Dasha Kumskova
Voronezh State Medical University named after N. N. Burdenko
Author for correspondence.
Email: dasha142430@yandex.ru
ORCID iD: 0000-0003-2518-3387
Russian Federation, 10 Studencheskaya str., Voronezh, Russia, 394036
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